1. Field of the Invention
The present invention relates to a curable composition, a pattern forming method, a pattern, and a method for manufacturing a device.
2. Description of the Related Art
An imprint method is a technique in which a mold having a pattern formed therein (which is generally referred to as a mold or a stamper) is pressed to transfer a micropattern onto a material. In a view that by using the imprint method, it is possible to fabricate a micropattern easily and accurately, it has recently been expected to be applicable to various fields. In particular, a nanoimprint technique in which a micropattern at a nano-order level is formed has attracted attentions.
As an imprint method, a thermal imprint method and a method called a photoimprint method have been proposed in terms of its transfer method. The thermal imprint method is a method in which a mold is pressed against a thermoplastic resin that has been heated to the glass transition temperature thereof or higher, and thereafter, the thermoplastic resin is cooled to the glass transition temperature or lower and then released from the mold to transfer a microstructure onto the resin on a substrate.
On the other hand, the photoimprint method is a method in which a curable composition is photo-cured under irradiation with light through a translucent mold or a translucent substrate, and the mold is peeled off so as to transfer a micropattern onto a photocured product. Since this method is an imprint for an uncured product, there is no need for heating at a high pressure and a high temperature, and it is possible to fabricate a micropattern easily. Further, since the method enables imprint at room temperature, it can be applied to a precision machining field for ultramicropatterns, such as manufacture of semiconductor integrated circuits.
Since the imprint method has a step of peeling a mold, it has had a problem in its releasability from the beginning. As a method for improving the releasability, a method in which the surface of a mold is subjected to a release treatment with a release agent such as a silane coupling agent having a perfluoroalkyl group is known. This method has a high effect of improving the releasability since it lowers the surface energy of the surface of the mold, but the release agent is deteriorated as the imprinting is repeated, and therefore, there has been a problem in durability.
JP2013-189537A discloses a curable composition for photoimprints having a high filling rate for a mold, a low release defect density, and high dry etching resistance, which contains a monofunctional monomer, a polyfunctional monomer, and a photopolymerization initiator, and has a viscosity of 15 mPa·s or less at 25° C., an Ohnishi parameter of 3.0 or less, and a crosslinking density of 0.6 mmol/cm3 or more.